ESTRO 2021 Abstract Book

S1017

ESTRO 2021

PO-1231 Response to neoadjuvant RCT as a predictor for overall survival in therapy of esophageal cancer S. Kirste 1 , F. Mohammad 1 , M. Murnik 1 , J. Höppner 2 , A. Grosu 1 , N. Nicolay 1 1 Medical Center – University of Freiburg, Faculty of Medicine, University of Freiburg, Germany, Department of Radiation Oncology, Freiburg, Germany; 2 Medical Center – University of Freiburg, Faculty of Medicine, University of Freiburg, Germany, Department of Surgery, Freiburg, Germany Purpose or Objective To evaluate the prognostic value of clinical parameters after neoadjuvant radiochemotherapy (RCT) and tumor regression grade (TRG) based on the Becker Score in squamous cell carcinoma and adenocarcinoma of the esophagus. Materials and Methods Patients undergoing trimodal treatment including neoadjuvant RCHT followed by esophagectomy between January 2009 and December 2017 were included. Influence of clinical parameters as well as TRG on overall survival (OS) was analysed. Univariate and multivariate analyses using log-rank and Cox proportional hazards models were performed and survival curves were estimated using the Kaplan-Meier method. Results Fifty-four patients with squamous cell carcinoma (70.4%) as well as adenocarcinoma (25.9%) of the esophagus were included in the analysis. Median age was 65 years. Most frequent tumor stage was cT3 (37 patients, 68.5%), and 44 patients (81.5%) had lymph node metastases. Neoadjuvant radiotherapy was performed with 41.4 Gy and either Cisplatin/5-FU in 28 patients (51.9%) or Carboplatin/Paclitaxel in 24 patients (44.4%). With a median follow-up of 37 months (range, 3-107), median OS was 66 months. Estimated 5-year- OS was 52%. The number of patients with TRG 1a, 1b and 2-3 according to Becker were 21 (38,9%), 16 (29,6%) and 16 (29,6%). 5-year-OS was 85%, 55% and 14% respectively (p<0.0001). Twenty-nine patients (53.7%) with initial lymph node metastases were downstaged to ypN0 after neoadjuvant RCHT. 5-year-OS was 75% for patients with ypN0 and 10% for patients with ypN+ (p< 0.0001). ypN status was also the strongest prognostic factor for OS in the multivariate analysis (HR = 3.03; p 0.027). Number of resected lymph nodes (<12 versus ≥12) had no influence on OS. In addition to TRG and ypN status, ypT stage (p< 0.0001), and L status (p< 0.0001) were significant factors in the univariate analysis whereas initial T or N stage or histology were not significant. Conclusion Response to neoadjuvant RCT as measured by TRG, ypT, ypN and ypL status, is an important factor for overall survival prediction. These parameters can potentially serve as criteria for patient selection for therapy intensification or organ-sparing approaches. PO-1232 Magnetic resonance-guided stereotactic body radiotherapy of liver tumors: Initial clinical experience and patient-reported outcomes F. Weykamp 1 , P. Hoegen 1 , S. Klüter 2 , K. Renkamp 2 , L. König 2 , K. Seidensaal 2 , S. Regnery 2 , J. Liermann 2 , C. Rippke 2 , S.A. Koerber 2 , C. Buchele 2 , J. Debus 2 , J. Hörner-Rieber 2 1 Heidelberg University Hospital, Radiooncology, Heidelberg, Germany; 2 Heidelberg University Hospital, Radiooncology, Heidelberg , Germany Purpose or Objective Stereotactic body radiation therapy (SBRT) has emerged as a valid treatment alternative for non-resectable liver metastases or hepatocellular carcinomas (HCC). Magnetic resonance (MR) guided SBRT has a high potential of further improving treatment quality, allowing for higher, tumoricidal irradiation doses whilst simultaneously sparing organs at risk. However, data on treatment outcome and especially patient acceptance is still scarce. Materials and Methods We performed a subgroup analysis of an ongoing prospective observational study comprising patients with liver metastases or HCC. Patients were treated with ablative MR-guided SBRT at the MRIdian Linac in the Department of Radiation Oncology at Heidelberg University Hospital between January 2019 and February 2020. Local control (LC) and overall survival (OS) analysis was performed using the Kaplan-Meier method. An in- house designed patient-reported outcome questionnaire was used to measure patients’ experience with the MR-Linac treatment. Toxicity was evaluated using the Common Terminology Criteria for Adverse Events (CTCAE v. 5.0). Results Twenty patients (with n=18 metastases; n=2 HCC) received MR-guided SBRT for in total 26 malign liver lesions. Median biologically effective dose (BED at α/β=10) was 105.0Gy (range: 67.2-112.5Gy) and median planning target volume was 57.20mL (range: 17.4-445.0mL). Median treatment time was 39.0min (range: 26.0- 67.0min). At 1-year, LC was 88.1% and OS was 84.0%. Gastrointestinal toxicity grade I° occurred in 30.0% and grade II° in 5.0% of the patients with no grade III° or higher toxicity. Overall treatment experience was rated positively, with items scoring MR-Linac staff’s performance and items concerning the breath hold process being among the top positively rated elements. Worst scored items were treatment duration, positioning and low temperature. Conclusion MR-guided SBRT of liver tumors is a well-tolerated and well-accepted treatment modality. Initial results are promising with excellent local control and only mildest toxicity. However, prospective studies are warranted to truly assess the potential of MR-guided liver SBRT and to identify which patients profit most from this new versatile technology. PO-1233 Real world results of CTRT in Ca esophagus: Can SCOPE-1 results be replicated outside trial setting? R. Sasidharan 1 , T. Bhattacharyya 1 , V. H Lal 1 , I. Mallick 1 , M. ArunSingh 1 , S. Chakraborty 1 , R. Basu Achari 1 , S. Chatterjee 1